Recently, an inkjet recording method is rapidly spread and more developed because material cost is low, high-speed recording is feasible, a noise is low while recording is performed, and color recording is easy.
The inkjet recording method includes a continuous manner that continuously disperses a liquid drop and an on-demand manner that disperses a liquid drop according to an image information signal as the inkjet recording method, and a discharging manner includes a manner that discharges a liquid drop by applying pressure by a piezo element, a manner that discharges a liquid drop by generating bubbles in ink by heat, a manner that uses an ultrasonic wave, and a manner that absorbs a liquid drop by electrostatic force and discharge it.
Further, an aqueous ink, an oily ink or a solid (melt type) ink is used as an ink for inkjet recording.
A colorant used in ink for inkjet recording needs to ensure favorable solubility or polydispersity to a solvent, recording at a high concentration, favorable colors, fastness to light, heat, and active gas (NOx, SOx other than oxidative gas such as ozone, or the like) in an environment, excellent fastness to water or chemicals, good settlement to an image-receiving material, low spreading, excellent preservation as ink, non-toxicity, high purity, and availableness at low price.
Various dyes and pigments have already been suggested for inkjet and have been used in practice, but an ink satisfying all requirements has not been found yet. It is difficult to combine color and fastness required to an ink for inkjet recording by using conventionally well-known dyes or pigments such as those with a color index (C. I.) number.
Recently, a disazo colorant, a trisazo colorant or a tetrakisazo colorant has been reviewed as a dye for black ink, but it has not satisfied a market demand for fastness to light and ozone gas.
Further, in addition to the above-mentioned points, the inkjet ink needs to ensure improvement of grey balance in a range from a high-concentration region to a low-concentration region from the viewpoint of image quality improvement of recorded matters obtained.